There is a need for effective pre-engagement detection of snipers because a single shot casualty of a high-value target is often sufficient to achieve the sniper's objective and there is often no intent to fire a second round. Pre-engagement cavity axis orientation measurement of snipers provides a proactive ability to eliminate or significantly reduce the threat of snipers by notifying the potential victim of the orientation of a sniper's weapon before the sniper shoots. What is needed is a technology capable of measuring the orientation of the longitudinal axis of a cavity so as to determine the intended target of a weapon whether it is direct (e.g., a rifle) or indirect fire (e.g., ballistic trajectory of a mortar or artillery shell).